There are a large number of rechargeable batteries having a wide variety of voltages and charging schedules. (Charging schedule, as used herein, is the manner in which the charging is performed for a given battery. For example, one charging schedule might call for a limited amount of current initially, and then a greater current when the battery voltage crosses a threshold, followed by a trickle charge after the battery voltage crosses a second threshold.) It is typical that a charger be designed for a single battery type, and have a single output voltage and charging schedule. Of course, dedicated battery chargers are not versatile, and can require a facility to have a number of chargers.
Other chargers are not dedicated, but are “dumb” chargers that apply a constant voltage output with the charging current being controlled by the load, not the charger. These chargers might work for any battery of a given voltage, but do not optimally charge batteries. Thus, if such chargers are used to charge several batteries simultaneously, they cannot provide a unique charging current or voltage for each battery. Rather, a single charging schedule is used for all batteries being charged. This also diminishes the usefulness of chargers.
Some battery chargers are inefficient because they have a poor power factor. This causes increased costs when power is utility power, and can lessen the charging capacity, particularly when using generator power. The use of generator power can cause another problem—generators often provide “dirty” power, i.e., power that is not perfectly sinusoidal, or not of a constant value. Dirty power can result in improper charging.
Prior art battery chargers are often design for a single input voltage and frequency. While this might be sufficient for consumer battery chargers, some applications, such as industrial battery charging, or automotive charging, might be used at different locations where the input power is not the same.
Rechargeable batteries have a finite life, in that their ability to be charged diminishes over time. Often, a user finds the battery is no longer chargeable by charging it, then using it, and having the battery become discharged in a short period of time.
Accordingly, a battery charger that is versatile enough to charge different types of batteries, or to simultaneously charge batteries with different outputs, is desirable. A modular design, where output circuits for particular batteries can be switched in and out by the user, is one manner to allow different charging schedules. Also, a single output module could be used for any battery type, where the user selects the battery type, or the charger senses the battery type. Preferably, such a charger will provide power factor correction, and be able to receive a wide range of inputs. Also, it will preferably be able to receive dirty power, and still charge a battery. A charger that provides the user a warning when a battery is defective is also desirable.